1. Field of the Invention
This invention relates to power supply apparatus used in an electronic apparatus like a television receiver, for example.
2. Description of the Related Art
Among recent television receivers and other electronic devices, those a remote-controller for improving the convenience have been distributed widely. Such a remote-controller includes a microprocessor as its central element, and includes various operation keys, encoder, light emitting section, and so forth. It is powered by a battery, for example, to code signals responsive to operation of various operation keys, output infrared control signals to an electronic apparatus to be controlled. In receipt of an infrared control signal, the electronic apparatus decodes the received signal and makes up detected information. Then, based on the detected information, it outputs a control signal for controlling each section and with a predetermined operation effected. For this purpose, such an electronic apparatus has a stand-by power supply in addition to its main power supply so that it can always cope with control signals sent from the remote-controller by supplying power to its photodetector and controller even when the power supply from the main power supply is stopped.
FIG. 9 shows a power supply apparatus of an electronic apparatus matching with a conventional remote-controller. In FIG. 9, a commercial alternating current (AC) is supplied to power input terminals shown by 101a and 101b. Numeral 108 denotes a rectifier bridge, and this rectifier bridge, smoothing capacitor and three-terminal regulator, which are not shown but connected to output terminals 109a and 109b, constitute a main power supply section.
Between the power input terminal 101b and the rectifier bridge 108, a main switch 103, a choke coil 106b and a switch 122a, forming a relay, are inserted in series.
Under the condition with the main switch 103 closed by manipulation of a user, when the switch 122a of the relay is turned ON, a rectified output is generated in the output terminals 109a and 109b, and smoothed, stabilized and thereafter supplied to a main load circuit, not shown.
On the other hand, numeral 121 denotes the load circuit of the control system. By making a standby power supply section from a voltage converting and rectifying circuit made up of an insulating transformer 111, rectifier bridge 112, three-terminal regulator 114 and two capacitors 113, 115, it is possible to supply a standby power supply to the control-system load circuit 121 and cope with a control signal sent from the remote-controller even when the relay switch 122a is turned OFF and the power supply from the main power supply is stopped.
When the main switch 103 is closed, a desired AC output is produced in the secondary coil 111b of the insulating transformer 111, and this AC output is full-wave-rectified by the rectifier bridge 112. Then, the full-wave-rectified output is smoothed by the capacitor 113, and a direct current (DC) stabilized in 5V, for example, is generated at the output terminal of the three-terminal regulator 114. This output voltage is supplied to LED 125, photodetector 126 and microcomputer 127, respectively, to activate the LED 125, photodetector 126 and microprocessor 127.